Pressure indicator for pneumatic tires



April 13, 1948. P. A. CRESSEY PRESSURE INDICATOR FOR PNEUMATIC TIRESFiled Aug. 8, 1944 4 Sheets-Shed 1 Inventor P5702 firms 6725.565);

April 13, 1948. P. A. CRESSEY PRESSURE INDICATOR FOR PNEUHATIC TIRESFiled Aug. 8, 1944 4. Sheets-Sheet 2 F2702 flmss 678E885);

April 1948- P. A. CRESSEY 2,439,561

PRESSURE INDICATOR FOR PNEUMATIC TIRES Filed Aug. 8, 1944 4 Sheets-Sheet3 Inventor Z3: 7-5/2 fi/VES 67255.95);

April 13, 1948. P. A. CRESSEY PRESSURE INDICATOR FOR PNEUMATIC TIRESFiled Aug. 8, 1944 4 Sheets-Sheet 4 tartan". E:

W V f I 6 Q A l i M C N 5 F 5 MIN mwfi W QMEQ E M E m N NW N QN bPatented Apr. 13, 1948 UNITED STATES PATENT OFFICE PRESSURE INDICATORFOR PNEUMATIC TIRES Peter Ames Creamy, McGrezor, Tex.

Application August 8, 1944, Serial No. 548,554

'2 Claims. ((71. 177-311) This invention relates to pressure indicatorsfor pneumatic tires and it has special reference to that type ofpressure indicator which is attached to a rotating wheel and is operatedby air pressure equal to that prevailing within the tire itself.

Pressure indicating devices for pneumatic tires as hitherto used aremainly of a type which is most suitable for high pressure tires in whichgreat differences of pressure are permissible. They operate by means ofa feeler, capped stud or the like applied against the wall of the tireand pressing or actuating an indicating plunger which is under springpressure. They have to be arranged, therefore, on the rim of the wheel.They have the advantage of avoiding connections which have to be sealedhermetically but they have the great disadvantage that the indication isfar from accurate and that they are merely able to indicate relativelygreat variations of pressure; moreover, the attachment of the indicatorto the rim of the wheel causes various difilculties as the influence ofthe centrifugal forces on the indicator is by no means negligible.

As it has been found that tire conservation is dependent on themaintenance of definite pressure within the tire which should varywithin narrow limits, more accurate indicating devices than those abovedescribed are necessary.

Indicating devices which can be arranged in the hub have been proposedbut theyhad the serious drawback that they required one or even severalmechanical seals in addition to the seal necessary for sealing the tireitself. As known in the art hermetic mechanical seals can be kept sealedonly with difilculty, if at all. At these imperfectly sealed places slowleaks develop so that the indicator becomes a permanent source oftrouble.

It is the main object of the present invention to overcome theinconvenience and difliculties associated with the known pressureindicators for tires and to provide an indicating device of highaccuracy, not influenced by the centrifugal forces due to the rotationof the wheel to which it is attached and with which it rotates and whichhas no mechanical seals other than those already employed which are aptto cause leakages.

A further object of the invention consists in providing a device of thetype indicated without frictional contacts which are in permanent useand which cause excessive wear and uncertain operation.

Further objects and advantages will be apparent from the detaileddescription of a modifica ing parts associated with the same.

Figure 5 is a plan view of the parts shown in Figure 4.

Figures 6 and '7 are a plan view and a side view, respectively, of thepressure chamber.

Figures 8 and 9 are plan views of several details.

m Figure 10 is a diagram illustrating an arrangement operated with A. C.mounted on the front wheel of a car, while Figure 11 is a similardiagram illustrating the same type of arrangement on the rear wheel of acar.

The general arrangement of a pressure indicator on a wheel is shown inFigure 1 of the drawings in which the reference numeral 5 indicates therim of a wheel on which a tire 2 whose pressure is to be supervised ismounted. The pressure indicator, generally indicated at 3, is mounted onthe hub portion i of the wheel preferably within the cap. covering thehub and wherever possible it is arranged centrally. Where centralarrangement is not possible the indicator may be arranged as closely asconveniently possible to the center as shown in Figure 1.

The indicator 3 is a self-contained unit preferably of cylindrical shapewith all its moving parts guided and arranged axially so that theyperform merely axial movement. The direct infiuence of the centrifugalforces on said movable parts is thus eliminated.

The pressure indicator comprises a cylindrical container 8 with a baseplate 3 having a concavely-shaped inner surface 9 and provided on on theoutside with flanges or lugs l, by means of which said container may befixed on the hub portion 4 of the wheel with its longitudinal axis atright angles to the plane of the wheel. Holes ill on said lugs 1 permitthe passage of the screw bolts (not shown) by means of which these partsare attached to each other. 7

In the lower portion of the cylindrical container a passage or duct 5 isarranged giving access to the interior of the container for a purpose tobe described.

Into the inner as well as into the outer side of the cylindrical wall ofthe container screwthreads I3 and I4, respectively, are cut, the latterengaging corresponding screw threads provided on the inside of adepending border flange or rim |2 of a cover or lid adapted to close thecontainer entirely when screwed on the same. Said cover is provided witha smooth central opening l5.

The screw-threaded part l3 provided on the inside of the cylindricalwall engages a screwthreaded ring or annular collar l6 with a centralopening I1. Between said collar i6 and the base plate 8 a pressure bagI9 is inserted, containing the pressure chamber 20 which is in permanentcommunication with the pressure space of the tire to be supervised. Thepressure bag I9 is preferably made of rubber or of similar elasticmaterial and it has the shape of a bladder with reinforced side wallsand a heavy peripheral rim. Its bottom part fits into the concave uppersurface of the plate 8 while its upper portion is firmly held at itsperipheral part by the collar or ring I6 which is screwed down to theextent required to obtain a firm gripping of the said peripheral part ofthe pressure bag between the collar and the base plate.

The pressure bag l9 is, moreover, provided with a tubular piece, pipe orhose 2 preferably integral with the bag itself, and made of the samematerial. the duct 5 in the container 6 which is provided for thispurpose and is joined, as shown in Figure 1, along a radial orapproximately radial line of the wheel with the valve receiving tubularstem 55 of the tire 2.

Preferably the valve is removed from the stem and one of the standardT-pieces 56 containing a valve and provided with two connections issubstituted. The stem 55 of the tire itself and the tubular piece 2| areboth screwed into the two openings of the T-piece 56, which carries thevalve. Both the stem and the tube 2| are sealed by the conventionalvalve. When the tire has to be removed the T-piece 56 with thevalve isunscrewed from the stem. In this way a single hermetic seal, such asusual in tires is provided for both the tire and the pressure chamber sothat the number of seals to be supervised is not increased by theindicator.

The pressure bag is is in permanent contact with a piston l8 resting onthe bag and pressed against it by means of a spring 22 which on theother side, finds its support on the lid or cover I I.

In its central part the piston l8 carries a rod 24 provided with screwthreads 25 which passes through the smooth opening l5 of the cover orlid H and which at its end carries a nut 26 of conducting material.

This nut cooperates with two contact strips 27,

28 which are fixed on the lid H and which are provided with bindingposts 29, 30 for making electrical connections. When the lid and thecontainer are made of insulating material the strips may be simply fixedto the surface of the lid. When these members are made of light metal orof an alloy, insulating strips (not shown) may be interposed between theconducting strips 21, 28 and the lid itself to prevent electricalcontact between these parts.

middle portion 32 and two straight side arms 33 and 34, one of said sidearms 38 is attached to the end of a metal rod 36 forming a long bindingpost running through an axial hole 31 in the cylindrical wall from oneend to the other. The end (not shown) of the rod 36 is connected withthat part which transmits current from the stationary frame of thevehicle to the rotating wheel. This current transmission is efiected inthe usual way by means of a brush 53a (Fig. 1) running on a contact ring53 or the like.

A screw 38 is carried by the top portion of the rod 35 and between itand the rod 36 one arm 34 of the bridge piece 3| is firmly held. Thesecond arm may rest on another screw 39 at the proper place in the endof the cylindrical wall of the container 6. It is, however, not fixedbut simply supports the bridge piece 3| on its head and prevents saggingwhen the pressure chamber is deflated.

The bridge piece 3| is connected with the piston l8 (Figures 4 and 5) bymeans of an annular sleeve 30, provided with internal screw threads,which engage corresponding screw This tubular piece 2| passes through ithreads 42 on the outer circumference of the piston i8. Small screwsd3arranged in a sufficient number connect the bridge piece 3| with thesleeve.

All the parts inserted between the rod 36 and the piston l8 as well asthe latter itself, are made of material which are good conductors ofelectricity, so that the current entering by means of the rod 36 canflow without resistance over the parts 3|, d3, to the piston I8, thecentral stem 25 and the nut 26.

It will be noted from the foregoing description that the movable partsare finely adjustable and that especially the air pressure at which theindicator becomes operative can be finely adjusted.

The piston H3 is held, guided and brought into Normally the piston |8rests on the pressure bag I9 which is inflated to such an extent thatthe spring 22 is compressed, while the unit 26 protrudes and is out ofcontact with the contact strips 2? and 28. The pressure which operatesthe alarm signal is, therefore, adjustable by means of the nut 26 but itcan also be adjusted by means of the lid or cover whose position may bechanged by screwing it down on the container 6 or by unscrewing it, anadjustment which will compress or expand spring 22.

The operation of the device will be clear from the above description ofthe parts. Assuming that D. C. from the battery of a vehicle(automobile, airplane) is used, the current path runs from groundedbattery 50 (Figure 1) over an indicating device 58 on the drivers orpilots dashboard and from there to a conta-ct'ring 53 and a brush 5311which is fixed on rod 35. The circuit then includes said rod 36, bridgepiece 3| fixed thereto to sleeve 4!), piston l8, stem 25 and nutzli. Theremaining part of the circuit includes the strips 27, 28 and the bindingposts 29, 30 which are connected with the body of the vehicle, usuallycalled ground.

The circuit thus consists of three parts separated by the two points ofconnections which are not permanent, one of these points is formed bythe brush 53a attached to rod 36 and the other point is the nut 26carried by the piston stem 25.

When the tire holds air of sufficlent pressure, the circuit is broken atthese two points as the piston is pressed towards the lid of thecontainer and thereby lifts the stem with the nut 26 and also holds therod 36 to which it is attached in a lifted position in which the brush53a does not touch the contact ring 53. I

when the tire is deflated, the piston is no longer held in the positiondescribed and the spring presses it against the deflated pressure bagI9. The nut 26 thus comes into contact with the strips 21 and 28 and thebrush 53a comes into contact with contact ring 53. The circuit is thusclosed and the annunciator device will operate.

The purpose of this arrangement resides in the separation of all movingcontacts during the period in which the tire pressure is normal; mere 1ywhen the pressure has fallen, the movable contacts come into contact.Thus, the annunciator device is free of parts which are in permanentfrictional contact and therefore practically free of parts requiringsupervision. v

Another method of avoiding the permanent frictional engagement ofcurrent carrying parts consists in the use of A. 0. induced in thewheel. Such an arrangement when adapted to operate on the front wheel ofa car is shown in Figure 10.

A front wheel, as well known, rotates on a fixed axle or cone. Thearrangement, according to the invention, consists of two separatecircuits, one of which is arranged on the vehicle body while the otheris mounted on the wheel. They are coupled in the following way.

On the axle close to the wheel, an inductor core to is arrangedpreferably with one of its legs centered in the axle'around which thewheel turns. Said core carries a primary winding H which is grounded orconnected with the body of the vehicle at 62 at one of its terminalswhile the other terminal 83 is connected with an insulated conductorleading to a vibrator GI, to an annunciator device 65 on the dashboardof the driver and to a battery 66, and from there to ground. On thewheel in front of the core 60, the core 61 is arranged with its legsfacing those of the core 60 and with as small an air gap as possibleleft between the legs of the two cores.

The core 61 is a small wheel with a rim t8 and a hub 69 projectingtowards the body of the vehicle and forming the legs of the core, whilethe "yoke is formed by the wheel disc of core 61. Said core is mountedpreferably with the axis of the small wheel forming one leg of the core,coinciding with the axis of the vehicle wheel and the secondary winding10 on said core is preferably wound around the central leg or hubportion 69. On the hub of the vehicle wheel (not shown in this figure)the container 8 with its lid II, the binding parts 29 and 30, thecontact .ctrips 21, 28, and the movable contact 25 is mounted. Thearrangement is identical with that described with reference to Figures 2to 5 with the exception that rod 36 is dispensed with.

One terminal of the secondary winding I0 is Y connected with the bindingpost 29 while the other is connected with the binding post 30. When thesecondary circuit is open at the contacts 21, 28, merely the pulsating,interrupted battery current is flowing through the primary circuit whichis insufficient to operate the indicator 65. When the pressure in thetire decreases as described in connection with Figures 2 to 5, themovable contact 26 will bridge the contacts 21 and 28. The secondarycircuit is closed and the primary current therefore is immediatelyincreased to such an extent that the indicator 65 will be operatedinstantly.

The arrangement shown in Figure 11 differs 6 from that in Figure 10mainly by the arrangement of those parts which form the cores of theinductor. As the rear wheels turn with their axle, the secondary coreconsists of a short length of said axle 13 forming the yoke" with twoannular collars or flanges 14 forming the legs" of the inductor core.

Opposing said legs the inductor core 15 carrying the primary winding 18is arranged on the housing Tl of the rear axle with its legs opposingthe collars I4 forming the legs of the secondary core. The windings l8,19 may be connected as before. It may, however, be preferable in somecases, as shown in the figure, to have a grounded secondary circuit andin this case the terminal of the secondary winding 19 and the terminal29 of the switch are grounded.

It will be seen from the above that the invention provides a reliableelectric alarm signal operated by contacts located within the rotatingwheel with a minimum of connection and with a continuous servicesubstantially without parts which are in permanent fixture.

The device is sealed in the same fashion in which the tires are sealedand does not obstruct the removal and replacement of the tire.

The indicating device is much more accurate adjustable thus permittingto establish narrow limits for the pressure to be maintained in the tireand to keep regularly within such limits.

It is to be understood that the invention resides broadly in thearrangement and in the combination of parts as described and illustratedand that the specification is to be understood as being illustrativeonly but not intended to limit the scope of the invention. Many changesmay obviously be made in the component parts and their assembly withoutin any way departing from the essence of the invention.

I claim:

1. In an indicator signal system for pneumatic tires mounted on rotatingwheels, a single circuit including a source of pulsating currents and asignal, the currents normally flowing in the circuit being incapable ofoperating the signal, means for increasing the ciu'rent flowing throughsaid circuit, said means comprising an inductor with a single windingarranged on the rotating wheel and a stationary single winding in closeproximity thereto, one of said windings being included in the aforesaidsingle circuit, a switch controlled short circuit for the other windingand pressure responsive means connected with the pneumatic tire forcontrolling the short circuit.

2. In an indicator signal system for pneumatic tires, mounted onrotating wheels, a rotating inductor, comprising a stationary iron core,with a winding thereon and a rotating iron core with a winding thereon,both arranged in close proximity to each other on the wheel and on a stationary part near the wheel respectively, a circuit containing a signaland a source of interrupted currents said currents when normally flowingin the circuit, being incapable of operating the signal connected withone of said windings, a pressure responsive switch and a circuitcontrolled thereby directly connected across the other winding forproducing a strong inductor current, means for connecting the pressureresponsive switch with the pneumatic tire under pressure and means tohold the pressure responsive switch in its open position when the tirepressure is normal. and to close it when the pressure falls below apredetermined limit.

PE'I'ER. AMES CRESBEY.

REFERENCES CITED The following. references are of record in' the file ofthis-patent: v

UNITED STATES PATENTS Number Name Date 1,882,681 Guthrie Oct. 18, 1932Number Number

